Abstract
Hybrid constructs represent substantial progress in tissue engineering (TE) towards producing implants of a clinically relevant size that recapitulate the structure and multicellular complexity of the native tissue. They are created by interlacing printed scaffolds, sacrificial materials, and cell-laden hydrogels. A suitable biomaterial is a polycaprolactone (PCL); however, due to the higher viscosity of this biopolymer, three-dimensional (3D) printing of PCL is slow, so reducing PCL print times remains a challenge. We investigated parameters, such as nozzle shape and size, carriage speed, and print temperature, to find a tradeoff that speeds up the creation of hybrid constructs of controlled porosity. We performed experiments with conical, cylindrical, and cylindrical shortened nozzles and numerical simulations to infer a more comprehensive understanding of PCL flow rate. We found that conical nozzles are advised as they exhibited the highest shear rate, which increased the flow rate. When working at a low carriage speed, conical nozzles of a small diameter tended to form-flatten filaments and became highly inefficient. However, raising the carriage speed revealed shortcomings because passing specific values created filaments with a heterogeneous diameter. Small nozzles produced scaffolds with thin strands but at long building times. Using large nozzles and a high carriage speed is recommended. Overall, we demonstrated that hybrid constructs with a clinically relevant size could be much more feasible to print when reaching a tradeoff between temperature, nozzle diameter, and speed.
Highlights
In tissue engineering (TE), the use of three-dimensional (3D) printing, known as additive manufacturing (AM), for the fabrication of scaffolds has steadily increased over the past few years [1,2,3].Many biocompatible materials have been successfully printed; one of the most outstanding synthetic resorbable polymers is polycaprolactone (PCL) due to its mechanical strength, stiffness, and tailorable degradation kinetics [5,6]
We studied the possible values of specific print parameters that could help in generating supporting structures of PCL for hybrid constructs while minimizing the print time
We found that the highest temperatures were in the middle of temperatures can be reached with the same band heater and using different materials for the carcass, the faces with clear hotspots in the lateral ones
Summary
In tissue engineering (TE), the use of three-dimensional (3D) printing, known as additive manufacturing (AM), for the fabrication of scaffolds has steadily increased over the past few years [1,2,3].Many biocompatible materials have been successfully printed; one of the most outstanding synthetic resorbable polymers is polycaprolactone (PCL) due to its mechanical strength, stiffness (enough to influence cell behavior [4]), and tailorable degradation kinetics [5,6]. PCL cannot be directly formulated with cells [7], but many in-vitro studies have shown clear cell spreading, attachment, and extracellular matrix formation over PCL scaffolds [2,8,9]. This biopolymer is easy to extrude due to its superior viscoelastic and rheological properties over many of its resorbable counterparts [10]. Conventional electrospinning is a simple and versatile process to produce 3D fibrous constructs with interconnected pores using a wide range of polymers These scaffolds have a high surface-area-to-volume ratio that mimics the natural extracellular matrix (ECM) [12]. Electrospun scaffolds have limitations in creating 3D structures of relevant physiological thickness [13]
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